Use MSBuild from the .NET SDK within Visual Studio

Right now Visual Studio uses its own copy of the MSBuild libraries, which can result in behavioral differences with the one that the user has brought with their SDK. To improve the consistency of results between the CLI and Visual Studio, we should align these versions in some way. An easy initial pathway would be to ship .NET Framework MSBuild in the .NET SDK, for example. Regardless, there will likely be work required to ensure compatibility between these disparate versions, which this issue will cover.

The issue names no files, tests, or entry points. Start by tracing how Visual Studio and the .NET SDK select MSBuild, then establish the compatibility constraints and a concrete definition of consistent behavior.

Written by the indexing model from the issue text.